Is This Fungus?

Today I noticed that there was a white edge on the tails of 2 of my black neons. One of them also has a bit of a white patch on the body. Is this fungus?

Thanks. I will probably just use some Melafix for now then and keep an eye on it.

I did my weekly water tests on that aquarium yesterday (the day before I do the water change). Ammonia and nitrite was 0, nitrate somewhere between 10 and 20 (those colours look very similar in the API test!), but it could be as high as 20!

I am trying to lower the nitrates using floating plants (which has worked very well in my other aquarium, nitrates are nearly 0) and added floating plants last week, but these are "1 2 Grow" lab grown plants so doubt that they have introduced anything into the tank.

I think the best thing to do in situations like this is a few extra water changes. Clean water often 'cures' simple problems. And when it's caused by nipping as in @fcmf 's feeding frenzy it also helps keep the damaged area clean.

The white patch on the body has completely disappeared now  . That fish and another one still have white on their fins so I will continue to treat the finrot with Melafix.